President Obama has called for a serious and reasoned debate about his plans to overhaul the health-care system. Any such debate must include the question of whether it is constitutional for the federal government to adopt and implement the president's proposals. Consider one element known as the "individual mandate," which would require every American to have health insurance, if not through an employer then by individual purchase. This requirement would particularly affect young adults, who often choose to save the expense and go without coverage. Without the young to subsidize the old, a comprehensive national health system will not work. But can Congress require every American to buy health insurance?
In short, no. The Constitution assigns only limited, enumerated powers to Congress and none, including the power to regulate interstate commerce or to impose taxes, would support a federal mandate requiring anyone who is otherwise without health insurance to buy it.
David B. Rivkin Jr. and Lee A. Casey - Constitutionality of Health Insurance Mandate Questioned - washingtonpost.com
I honestly can't answer the question of how the Supreme Court would rule, they love to wrap stuff up in the commerce clause. However, suppose someone files suit (they will) and it goes to the SC and is ruled unconstitutional? I wonder if the entire bill would be revoked or just the mandate? If it's just the mandate, I wonder how that effects the cost. Wish the CBO would do a study on the current compromise plan in the Senate sans the mandate.